Marine Heatwaves’ Impacts on Marine Organisms

Prolonged heatwaves can have serious implications for humans, animals and landscapes, and there's mounting evidence that periods of unusually high sea temperatures can severely harm marine ecosystems. However, measuring the impacts on marine life has proven challenging because existing methods do not integrate the physiological responses of a marine organism across the many different intensities and lengths of heatwaves that are increasingly occurring. Recent research at the University of New Hampshire and New Hampshire Agricultural Experiment Station has shown that when both components are accounted for, the results provide more detailed assessments of marine heatwave impacts and may help in developing more effective mitigation strategies.

To address this, recently published research by Easton White, a scientist with the New Hampshire Agricultural Experiment Station, and Andrew Villeneuve, a Ph.D. student in UNH's marine biology program, used simulations to create a new framework that assesses the deadly effects of marine heatwaves based on organismal response.

"Traditional statistical methods fall short because they ignore the biological responses of organisms," explained Easton White, Station scientist and assistant professor in the department of biological sciences at UNH. "Our physiological framework, which we present in this paper, considers how marine organisms respond to both the intensity and duration of heat stress, offering a much clearer understanding of the lethal impacts of marine heatwaves."

He added, "This approach is crucial for predicting how these extreme events will affect marine ecosystems and for developing strategies to mitigate their effects."

White and Andrew Villeneuve, a Ph.D. student in the UNH marine biology program, published their findings in the Journal of Animal Ecology earlier this year. The paper describes simulation models using three aquatic mollusk species exposed to varying degrees of heat tolerance. The findings show that both short, intense heatwaves (acute events) and longer, milder heatwaves (chronic events) can be equally deadly to marine organisms. The results advance existing research and monitoring efforts by focused highlighting that the more frequent, short bursts of extreme heat can be just as harmful as longer heatwaves.

"By understanding the specific survival thresholds for different marine species, our research can provide insight into how various heatwave profiles impact marine life," said Villeneuve. "This understanding is key for developing more effective conservation and management strategies to protect vulnerable marine ecosystems."

Villeneuve added, "For instance, if a specific marine species is found to be highly susceptible to short, intense heatwaves, conservation measures might focus on creating refuges or cooler microhabitats during these peak heat periods to help ensure their survival."

The importance of a more physiological framework will become essential as climate change and ocean warming continue, added White. Future research will focus on validating these models in a lab and better understanding how marine species acclimate to different heat conditions over varying periods.

"Moreover, integrating these dynamic thermal tolerance models with other ecological models will offer a more comprehensive view of how marine heatwaves affect our entire ecosystems," said White.

The team also recently published related work on modeling the effects of extreme events on ecological systems.

This work is co-authored by Andrew Villeneuve and Easton White.

This material is based on work supported by the NH Agricultural Experiment Station through joint funding from the USDA National Institute of Food and Agriculture (under Hatch award number 7005066) and the state of New Hampshire.

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